Combustion Noise from Non-premixed and Lean-premixed Swirl Flames

Abstract

The development of modern gas turbines and jet engines is focused on the reduction of pollutant emissions and, increasingly, on the reduction of overall noise emission, including combustion noise. This requires the minimization of the noise sources, namely noise from the turbulent flow, combustion noise and noise caused by periodic instabilities and fluctuations of the ignition zone. This has to be achieved under conservation of the benefits of swirl flames, e.g. high ignition stability and broad operation ranges. This paper is focused on the description and characterisation of fluctuations of the ignition zone due to different mixing and stabilization characteristics of noise from swirl flames. Another goal was the description of flame noise caused by the formation and burning of coherent, periodic flow structures, often detected in swirl flows and flames [1, 2, 3, 4]. The physical model offers the possibility to understand the formation mechanism of the coherent flow structures and their effect on the combustion of non-premixed and premixed swirl flames.